1. Field of the Invention
The present invention relates to a fuel injection apparatus used for an internal combustion engine.
2. Description of the Related Art
A fuel injection apparatus using an ordinary fuel injector to feed fuel to an internal combustion engine (engine) pressurizes the fuel using a fuel pump in order to obtain the fuel injection pressure. A certain time is required in this case in order for the fuel to be injected to be pressurized to the prescribed pressure from when the driver turns the ignition switch on and the fuel pump starts operating at the time of startup of the engine.
Therefore, when the fuel injectors start injecting fuel in the state immediately after the start of the startup operation of the engine when the fuel has not yet been pressurized to the prescribed pressure, there is insufficient atomization of the injected fuel. Further, since the amount of injection is difficult to control in a state where the injection pressure has not reached the prescribed value, the problems of poor startup of the engine and an increased emission of hydrocarbons arise. Also, since the time required for pressurization of the fuel increases in proportion to the magnitude of the pressure in an engine injecting high pressure fuel, the above problems become even more serious.
When the engine is extremely cold, further, the voltage of the battery falls, so the performance of the battery-driven fuel pump falls as well. Also, the start motor, which is again driven by the battery, fails to turn strongly. Accordingly, the cranking speed becomes lower than during an ordinary temperature resulting in poor or failed startup in some cases.
Note that Japanese Unexamined Patent Publication (Kokai) No. 56-146051 discloses a fuel injection control apparatus designed to reduce the engine startup time by providing a switch attached to a door key, a door switch, a seat switch attached to the seat, or other "switch operated before startup" in parallel with the ignition switch, starting the driving of an electric fuel pump by the "switch operated before startup" before the driver turns the ignition switch on as the normal means of starting the engine, and thereby pressurizing the fuel to be injected in advance. In this case, however, the ordinary battery driven electric fuel pump is driven before the startup operation, so when the battery performance falls such as at extremely cold periods, there is again the problem of poor startup.